Time-domain studies of M31

Figures & data

Figure 1. Footprints of distance indicator surveys – the DIRECT (cyan squares) and the WFCAM/INT (red square) surveys. .

Note: The underlying image comes from the UV space telescope Galaxy Evolution Explorer (GALEX [9])

Figure 2. Footprints of high-cadence microlensing surveys – the POINT-AGAPE (green squares), WeCAPP (yellow square), and POMME (red squares) survey. .

Note: The underlying image comes from the infrared space telescope Wide-field Infrared Survey Explorer (WISE, [23])

Figure 3. Variables from POINT-AGAPE surveys.

Note: The two boundaries are R[mag] = 25 – 3log and R[mag] = 32.2 – 6log, separating the variables into classical Cepheids (left), population II Cepheids (middle) and LPVs (right) in the period-luminosity plot.

Figure 4. Classical Cepheids PL relation. Left: r-band mean-phased photometry from ground-based PS1 telescope. The photometry is heavily effected by the blending effects. Right: J-band random-phased photometry from Hubble Space Telescope. The exquisite spatial resolution delivered by HST enables us to get rid of the blending effects.

Note: The Cepheids light curve amplitude is relatively small in the infrared than in the optical band, so even random-phased photometry yields very clean PL relation.

Figure 5. Beat Cepheids in M31, M33, Milky, and Magellanic Clouds. Left panel: period v.s. period ratio of the beat Cepheids over-plot on the lowest possible metallicity tracks. Right panel: period v.s. period ratio of the beat Cepheids over-plot on the highest possible metallicity tracks.

Figure 6. Radial velocity and light curves of the 2 eclipsing binaries used by Ribas et al. [20] (left) and Vilardell et al. [21] (right) to derive an independent, direct M31 distance to 4%.

Figure 7. R Coronae Borealis light curve from AAVSO.

Figure 8. Microlensing light curve of POINT-AGAPE-S3/WeCAPP-1. Data points are POINT-AGAPE r-band (green), POINT-AGAPE i-band (orange), WeCAPP R-band (blue), and WeCAPP I-band (red).

Note: The best-fit microlensing model is over-plotted in black line.

Figure 9. An M31 exoplanet microlensing candidate light curve in (upper), (middle), and -band (bottom panel), over-plotted with the best-fit binary lens model C1 with a mass ratio of 0.014 [83].

Figure 10. Upper panel: light curves of S-type novae. Lower panel: light curves of C-type novae.

Figure 11. Upper panel: light curve of an M31 J-type nova (M31N 2001-10a). Lower panel: time intervals between the peak of successive jitters v.s. time intervals between each jitter and the time of eruption. There is a trend in the log–log plot, consistent with the hydrogen burning envelope instabilities scenario [102].

Figure 12. The infrared PL relation as seen from M31. The sample is obtained from LMC long-period variables, with magnitudes scaled to the distance of M31. We can see several long-period variable tracks, such as A, B, C, and D as shown in Ita et al. (2004, [105]), are all brighter than K = 19 mag, hence feasible with 4-m class telescopes on the ground.

Note: The G and F tracks mark the classical and population II Cepheids.

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